The answer to how Covid 19 is spreading in South Africa might be found in sewage
Recent research has shown the presence of Sars-Cov-2 nucleic acids in the faeces of infected people and wastewater from infected communities, according to the Water Research Commission (WRC), though no infective strain has been confirmed.
There’s increased interest, it says, in the presence and persistence of the virus in the “water and sanitation environment, the role of the aquatic environment in the transport and possible transmission through exposure to contaminated surface water sources, poorly treated municipal wastewater and the faeces of infected people”.
Last week, it unveiled a national wastewater-based epidemiological study for the surveillance of Covid-19 spread in communities. “This could provide a rapid and effective way to predict the potential spread of Covid-19 by picking up on biomarkers in faeces and urine from disease carriers that enter the sewer system.”
Rapid testing kits using paper-based devices could be used on-site at wastewater treatment plants to trace sources and determine whether there are potential Covid-19 carriers in areas.
“This could lead to an early warning system for Covid-19 in any second- or third-wave predictions and provide preparedness for future pandemics.”
The WRC’s Nonhlanhla Kalebaila and Stanley Liphadzi explain how developing countries might not be able to afford or implement mass-screening programmes to uncover new infections, a “huge challenge as the pandemic peaks”.
“However, there is an opportunity of tracing of Covid-19 spread in sewered wastewater treatment systems and non-sewered sanitation systems. This promises to provide us with information that could track and signal hot spots of community transmission.”
The virus is shed primarily from the respiratory and gastrointestinal tract.
“Studies suggest that coronaviruses may survive in stool samples for three to four days. Interconnectedness of the wastewater plumbing network can facilitate exposure, as in Hong Kong.”
Professor Anthony Turton of the University of the Free Sate’s centre for environmental management says the major risk arising from Covid-19 is the fact that people can be infected but show no symptoms. Since the government cannot test every citizen in the country, sewage surveillance is key.
“We have 824 wastewater treatment works in South Africa. Each of these serves a population of known size.
“By taking samples of sewage according to a defined protocol, it is now technically possible to determine the viral load of the entire population in the catchment area of that sewage works. This data can be compared weekly, and from this we can determine if the total viral load is increasing or decreasing.”
This is much easier than individual testing of millions of citizens, “the results of which only give a snapshot of information relevant to those specific people at that precise moment in time”.
There’s a traceable presence of the virus in both urine and faeces before a patient manifests with symptoms and after a patient has been treated.
“This does not mean that the virus is still infectious, although there is some mention of faecal-oral transmission in peer reviewed literature, at least of the Sars virus.
“This is not yet fully understood, so the faecal-oral transmission pathway is mostly ignored by policy response, which is typically based on Western premises such as a fully functional wastewater works. That may not be the case in developing countries, but the jury is still out on the faecal-oral transmission route.”